Method of producing a transmissive screen and the transmissive screen

ABSTRACT

The invention provides a method of producing a transmissive screen having a structure including light-absorption-material patterns that are formed on locations corresponding to locations of lens members, which are provided side by side on a light-transmissive substrate, and to locations of boundary portions between the corresponding lens members. In this method, lens compositions are discharged onto and are caused to land on the light transmissive substrate, and, by drops of the lens compositions, very small lens members or precursors thereof are formed. It is possible to provide a method of producing a transmissive screen, which makes it possible to realize, at a low cost, a bright transmissive screen which has high contrast ratio and which can display a high-quality image having reduced or no moiré and reduced or no speckles.

This is a Continuation Application of application Ser. No. 10/069,756filed Feb. 28, 2002, now U.S. Pat. No. 6,621,637, which in turn is aNational Stage of International Application No. PCT/JP01/05774 filedJul. 3, 2001. The entire disclosure of the prior applications are herebyincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a projection screen technology, andmore particularly, to a method of producing a transmissive screen usedas a display screen of a projection television or a microfilm reader,for example. The invention also relates to a transmissive screenproduced by this method.

2. Description of Related Art

In recent years, rear projectors that use a liquid crystal light valveor a CRT as a large screen display have been the focus of attention. Thedisplay displays an image by forming an image on a transmissive screenusing image light from an image projecting portion. This type oftransmissive screen is bright when an observer observes the image andhas predetermined very small lens members formed thereon so as toincrease the viewing angle.

As shown in FIG. 11, with regard to light distribution property of sucha bright screen that has a wide viewing angle, a viewing angle 1101,which is wider in the horizontal direction than in the verticaldirection, is preferred. This is because the viewing angle of a humanbeing is wider in the horizontal direction than in the verticaldirection. When the light distribution is made to be equal in thevertical and horizontal directions, light is also distributed in thevertical direction which is not actually necessary with regard to theviewing angle of a human being, so that the brightness as a whole isreduced.

Representative examples of the structures of the transmissive screeninclude the following:

{circle around (1)} A lenticular sheet includes a lens portion that isformed by providing convex cylindrical lenses (semi-circular cylindricalconvex lenses) side by side. As shown in FIG. 9(a), in general, thelenticular sheet has a structure that is formed by forming both surfacesof the sheet into convex cylindrical lens surfaces 901, formingprotrusions at boundary portions between the respective cylindricallenses at one of the surfaces of the sheet (the surface from which imagelight 201 exits), and forming a light-shielding layer (a black stripehaving a light-absorption property) 902 on the top portion of each ofthe protrusions.

The lenticular sheet is obtained by performing a press-molding operationon a transparent thermoplastic resin sheet or by molding both surfacesof the resin sheet at the same time that molten extrusion is performed.

{circle around (2)} A planar lens has very small transparent ballsarranged two-dimensionally (disclosed in, for example, U.S. Pat. Nos.2,378,252 and 3,552,822, and Japanese Utility Model Registration GazetteNo. 2513508). As shown in FIG. 10(a), in the planar lens, each of thevery small transparent balls 1002 has approximately 50% of its diameterembedded in, and held by, a light-incident side transparent layer 1001,and the remaining approximately 50% embedded in a light-exiting sidelight absorption layer 1003.

The planar lens is obtained by forming a sheet that includes atransparent layer, very small transparent balls, and a light-absorptionlayer, and then bonding it to a transparent substrate 1004.

However, such related art transmissive screens are subject to thefollowing problems.

In the lenticular lens, it is difficult to achieve a fine pitch wheneach of the above-described molding methods is performed onthermoplastic resin, so that when the lenticular lens is used as ascreen of a rear projector, which in recent years has been used toprovide increasingly higher definition, there is a problem in thatdeterioration of image quality occurs due to reduced resolution andproduction of moiré. In addition, a very small light diffusing materialis typically mixed in the inside portion of the lenticular lens in orderto increase the viewing angle in the vertical direction (a directionparallel to the lenticular lens, which is represented by referencenumeral 903 in FIG. 9(b)) in which the lenticular lens does not haveoptical power. This gives rise to the problem that image quality isdeteriorated because speckles are produced due to the interference ofimage light caused by the light-diffusing material. Further, both of themolding methods performed on the thermoplastic resin require largemolding machines or dies having diagonals that are equal to or greaterthan 50 inches, which are of the same size as the screen of the rearprojector, giving rise to the problem that production costs become veryhigh.

On the other hand, in the planar lens having very small transparentballs that are arranged two-dimensionally, as shown in FIG. 10(b) inwhich the planar lens is viewed from an image light incident side, deadspaces, which do not pass image light, are formed between the individualvery small balls 1002, so that the image light incident thereupon is nottransmitted to the observer side. In addition, it is very difficult tocompletely perform a minute filling operation with respect to the verysmall balls, so that the dead spaces increase in size. Further, sincethe thin light absorption layer 1003 remains at the observer-sidesurfaces of the very small transparent balls, light is absorbed. Due tothese three reasons, the problem arises that light transmittance of thetransmissive screen is low.

Since the increase in the viewing angle by the very small balls iscompletely isotropic, light is also diffused in the vertical direction,in which the viewing angle does not normally need to be increased verymuch, to the same extent as in the horizontal direction. This gives riseto the problem of insufficient brightness when the image is viewed fromthe front.

In general, the planar lens is produced by the step of forming a sheetincluding a transparent layer, very small transparent balls, and a lightabsorption layer, and bonding the sheet to a transparent substrate.However, in the step of bonding the sheet to the transparent substrate,unevenness in the bonding occurs, so that the display of the imagebecomes non-uniform, and by insufficient adhesiveness between the sheetand the transparent substrate, interfacial multiple reflection occurs,thereby giving rise to the problem of reduced resolution.

SUMMARY OF THE INVENTION

In order to address the above-described problems, it is an object of thepresent invention to provide a method of producing, at a low cost, atransmissive screen which is bright, which has high contrast andresolution, and which is capable of displaying a high-quality imagewithout or with reduced moiré and scintillation.

In order to address the above-described problems, a first aspect of thepresent invention provides a method of producing a transmissive screenhaving a structure that includes light-absorption-material patternsformed at locations corresponding to locations of lens members, whichare provided side by side on a light-transmissive substrate, and tolocations of boundary portions between the corresponding lens members.The method includes the step of forming the lens members or precursorsthereof by causing very small drops of lens compositions to bedischarged and to land near a light-transmission area on a surface ofthe light-transmissive substrate. An inkjet recording head causes thevery small drops of the lens compositions to be discharged and to land.Preferably, the inkjet recording head is a piezo jet recording head.

According to this aspect, the individual lens members, formed on thesurface of the transmissive screen, are formed by the discharging oflens compositions from an inkjet recording head, typified by, forexample, a piezo jet recording head, having the excellent feature offorming a very fine form with high precision over a large area.Therefore, very fine lens members can be produced. Consequently, it ispossible to provide a transmissive screen which provides excellentresolution and which does not have or lessens reduced image quality dueto moiré. In addition, this method can be used in producing atransmissive screen by a manufacturing device including a mechanism thatscans the piezo jet recording head in the horizontal/vertical directionsof the screen. Therefore, the required use of expensive manufacturingdevices, such as large dies and molding devices, is reduced or obviated,thereby making it possible to reduce production costs.

In a second aspect of a method of producing a transmissive screen inaccordance with the present invention, the surface form of each of thelens members is restricted by adjusting the surface tension andviscosity of each of the lens compositions, and the wettability of eachof the lens compositions and a surface which each of the lenscompositions contacts.

According to this aspect, a processing operation using a die is notrequired, so that the forms of the lens members can be controlled by asimple step, thereby making it possible to reduce production costs.

A third aspect of a method of producing a transmissive screen inaccordance with the present invention includes the step of forming thelight-absorption-material patterns into the shape of a bank on a surfaceof the light-transmissive substrate prior to forming the lens membersand the precursors thereof by causing the very small drops of the lenscompositions to be discharged and to land near a light-transmissionportion of the bank-shaped light-absorption-material patterns.

According to this aspect, the lens resin compositions are dischargedonto the vicinity of the light-transmission portions of the bank-shapedlight-absorption-material patterns in order to form the lens members, sothat the light-absorption-material patterns and the lens members arealigned with high precision, thereby increasing the light transmittanceof the transmissive screen.

In a fourth aspect of a method of producing a transmissive screen inaccordance with the present invention, the surface of thelight-transmissive substrate on which the light-absorption-materialpatterns are formed is different from the surface where the lens membersare formed.

According to this aspect, it no longer becomes necessary to consider thechemical reaction between the light-absorption-material-patterncompositions and the lens member compositions, thereby increasing thevariety of materials from which selection can be made, so that it ispossible to provide a low-cost transmissive screen using low-costmaterials.

In a fifth aspect of a method of producing a transmissive screen inaccordance with the present invention, the light-absorption-materialpatterns or precursors thereof are formed by causing very small drops oflight-absorption-material pattern compositions to be discharged and toland. An inkjet recording head causes the very small drops of thelight-absorption-material pattern compositions to be discharged and toland. Preferably, the inkjet recording head is a piezo jet recordinghead.

According to this aspect, since the light-absorption-material patternsand the lens members can be formed by the method of discharging verysmall drops and causing them to land, the production process issimplified, thereby making it possible to provide a low-costtransmissive screen.

In addition, since the light-absorption-material patterns are formed bydischarging the light-absorption-material-pattern compositions from theinkjet recording head, typified by, for example, a piezo jet recordinghead, having the excellent feature of forming a very fine form with highprecision over a large area, it is possible to form very finelight-absorption-material patterns. Therefore, it is possible to providea transmissive screen which provides excellent resolution and which doesnot have or lessens reduced image quality due to moiré. Further, thismethod can be used to produce a transmissive screen by a manufacturingdevice including a mechanism that scans the piezo jet recording head inthe horizontal/vertical directions of the screen. Therefore, expensivemanufacturing devices, such as large dies and molding devices, are notrequired, thereby making it possible to reduce production costs.

A sixth aspect of a method of producing a transmissive screen inaccordance with the present invention includes the step of restricting aplanar form of each of the lens members on the surface of thelight-transmissive substrate situated at the side where the lens membersare formed prior to forming the lens members or the precursors thereof,with the restricting operation being a chemical operation or arestricted form formation operation, which restrict spreading of thelens member compositions on the transparent substrate.

According to this aspect, since the forms of the lens members can becontrolled without using a die, it is possible to produce a transmissivescreen having any viewing angle at a low cost.

In a seventh aspect of a method of producing a transmissive screen inaccordance with the present invention, the step of restricting theplanar form of each of the lens members is the same as the step offorming the light-absorption-material patterns.

According to this aspect, it is possible to omit additional steps ofrestricting the planar forms, so that the process can be simplified.

In an eighth aspect of a method of producing a transmissive screen inaccordance with the present invention, adjacent lens members are formedof different lens member compositions. Preferably, the different lensmember compositions are adjusted so as to not or only slightly mix witheach other.

According to this aspect, since the adjacent lens member compositionsmay be those that do not mix easily with each other, it is possible toreduce the distances between the adjacent lens members, so that deadspaces become smaller. Therefore, it is possible to realize atransmissive screen having high light transmittance.

A transmissive screen in accordance with an aspect of the invention isproduced by any one of the methods of producing a transmissive screen.

According to this aspect, the individual lens members, formed on thesurface of the transmissive screen, are formed by the discharging oflens compositions from an inkjet recording head, typified by, forexample, a piezo jet recording head, having the excellent feature offorming a very fine form with high precision over a large area.Therefore, very fine lens members can be produced. Consequently, it ispossible to provide a transmissive screen which provides excellentresolution and which does not have reduced image quality due to moiré.In addition, in this aspect, this method can be used in producing atransmissive screen by a manufacturing device including a mechanism thatscans the piezo jet recording head in the horizontal/vertical directionsof the screen. Therefore, the required use of expensive manufacturingdevices, such as large dies and molding devices, is reduced or notrequired, thereby making it possible to reduce production cost, and thusto provide a low-cost transmissive screen.

In a second form of a transmissive screen of the present invention,spectral characteristics of the light-transmissive substrate, each ofthe lens members, and each of the light-absorption-material patterns,are substantially uniform or smooth in light transmission or lightabsorption properties in the visible region.

According to this aspect, since the color of the display image can beeffectively reproduced, it is possible to realize a transmissive screenwhich can display a high-quality image.

In a third aspect of a transmissive screen of the present invention, theform of the bottom side of each of the lens members to be formed issubstantially rectangular.

According to this aspect, since the bottom side forms of the individuallens members are substantially rectangular, when the individual lensmembers are subjected to a filling operation performed with closeattention, dead spaces between the individual lens members are notgenerated. Therefore, it is possible to realize a bright transmissivescreen having high light transmittance.

In a fourth aspect of the transmissive screen of the present invention,where the radius of curvature of each of the lens members, which is tobe formed, in a horizontal direction of the transmissive screen is RH,and the radius of curvature of each of the lens members, which is to beformed, in a vertical direction of the transmissive screen is RV, RH<RV.

According to this aspect, since the optical power of each lens member inthe horizontal direction is greater than the optical power of each lensmember in the vertical direction, the viewing angle of the transmissivescreen in the horizontal direction can be made to be larger than theviewing angle of the transmissive screen in the vertical direction.Therefore, it is possible to adequately diffuse image light which haspassed through the transmissive screen in the proper direction inaccordance with the viewing angle characteristic of a human being.Consequently, a bright transmissive screen can be realized.

In a fifth aspect of a transmissive screen of the present invention,where the width of each of the lens members, which is to be formed, in ahorizontal direction thereof is WH, and the width of each of the lensmembers, which is to be formed, in a vertical direction thereof is WV,WH<WV.

According to this aspect, where the form of the surface of each lensmember is restricted by adjusting the surface tension and viscosity ofeach of the lens compositions and the wettability of each of the lenscompositions and a surface which each of the lens compositions contacts,the radius of curvature of the larger-width portion of each lens memberbecomes large and that of the smaller-width portion of each lens memberbecomes small. When this is examined from the point of view of opticalpower, the smaller radius of curvature corresponds to the larger opticalpower. Therefore, by causing the horizontal-direction width of each lensmember to be smaller than the vertical-direction width thereof as inthis aspect, the optical power in the horizontal direction becomeslarger than that in the vertical direction, so that the viewing angle ofthe transmissive screen in the horizontal direction can be made largerthan that of the transmissive screen in the vertical direction.Therefore, it is possible to adequately diffuse image light which haspassed through the transmissive screen in the proper direction inaccordance with the viewing angle characteristic of a human being.Consequently, a bright transmissive screen can be realized.

In a sixth aspect of a transmissive screen of the present invention, thedistances between adjacent landing target locations of the lenscompositions are not uniform in a plane of the transmissive screen.

According to this aspect, since the lens members are not disposed at thetransmissive screen in a regular manner, it is possible to enhance thequality of a projected image with reduced moiré.

In a seventh aspect of a transmissive screen of the present invention,the distances between the adjacent landing target locations of the lenscompositions in a horizontal direction, and those in a verticaldirection are different. Preferably, where the distances in thehorizontal direction are PH, and those in the vertical direction are PV,PH>PV. More preferably, where the diameter of a single lens member isSP, the distances between the adjacent landing target locations of thelens compositions are such that PH>SP>PV.

According to this aspect, it is possible to fuse adjacent lens membersin the vertical direction. The resulting compound lens member obtainedis such that its vertical-direction radius of curvature is larger thanthe horizontal-direction radius of curvature, so that it is possible forthe horizontal-direction viewing angle of the transmissive screen to begreater than the vertical-direction viewing angle of the transmissivescreen.

A ninth aspect is provided of a method of producing a transmissivescreen having a structure including light-absorption-material patternsthat are formed on locations corresponding to locations of lens members,which are provided side by side on a light-transmissive substrate, andto locations of boundary portions between the corresponding lensmembers. The method includes the step of forming volume-type phasedevices or precursors thereof by causing very small drops of volume-typephase device compositions to be discharged and to land, with thevolume-type phase devices having random phase distributions beingprovided side by side on a surface of the light-transmissive substratewhere the lens members are formed or the back side of the surface. Aninkjet recording head causes the very small drops of the volume-typephase device compositions to be discharged and to land. Preferably, theinkjet recording head is a piezo jet recording head.

According to this aspect, volume-type phase devices having random phasedistribution are provided side by side on the back side of alens-formation surface of the light-transmissive substrate. Sinceinterference is reduced by randomly disturbing a wave surface of imagelight, speckles can be considerably reduced. In addition, since thevolume-type phase devices are formed by using an inkjet recording head,typified by a piezo jet recording head, production costs can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a)-1(d) are schematics illustrating the steps of a firstembodiment of a method of producing a transmissive screen in accordancewith the present invention;

FIGS. 2(a) and 2(b) are a plan view and a sectional view of thestructural elements used in the first embodiment;

FIGS. 3(a)-3(c) are schematics illustrating the light distributionfunction of a lens member used in the first embodiment;

FIGS. 4(a)-4(b) are schematics illustrating the steps of a secondembodiment of a method of producing a transmissive screen in accordancewith the present invention;

FIGS. 5(a)-5(d) are schematics illustrating the steps of a thirdembodiment of a method of producing a transmissive screen in accordancewith the present invention;

FIGS. 6(a)-6(c) are schematics illustrating a gap between adjacentlanding target locations and the planar form of a lens member to beformed in the third embodiment;

FIGS. 7(a) and 7(b) are schematics illustrating a gap between some otheradjacent landing target locations and the planar form of the lens memberto be formed in the third embodiment;

FIGS. 8(a) and 8(b) are schematics illustrating the steps of a fourthembodiment of a method of producing a transmissive screen in accordancewith the present invention;

FIGS. 9(a) and 9(b) are schematics of a lenticular lens sheet;

FIGS. 10(a) and 10(b) are schematics of a planar lens; and

FIG. 11 is a schematic illustrating the light distribution of atransmissive screen.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Hereunder, with reference to the drawings and the like, a detaileddescription will be provided by providing embodiments of the presentinvention.

(First Embodiment of a Method of Producing a Transmissive Screen)

FIGS. 1(a)-1(d) are schematics generally illustrating a generalizationof the steps used in the first embodiment.

First, as shown in FIG. 1(a), a light-absorption material 102 issubjected to a patterning operation to be a desired form on alight-transmissive substrate 101. It is desirable that thelight-transmissive substrate 101 have a substantially uniform lighttransmittance property over the entire visible region and that thislight transmittance be high. The light-transmissive substrate 101 may bemade to have light diffusion property by diffusing very small,diffusible particles in the substrate or by forming the surface thereofas a diffusing surface. In addition, it is preferable to form thelight-transmissive substrate 101 with a rigid material that can maintaina uniform or smooth light transmissive property when it is incorporatedin a rear projector. Examples of such a rigid material are transparentglass substrate and acrylic substrate, but are not limited thereto.

Similarly, it is preferable for the light-absorption material 102 to bea material having a substantially uniform or smooth absorption propertyover the entire visible region, and for the light transmittance of thematerial to be low. The characteristics of the material are selected byconsidering various characteristics from the viewpoints of thepatterning method used and chemical interactions between lens members.

Examples of methods of patterning the light-absorption material 102include photolithography and various other printing techniques, and amethod in which a light-absorption material compositions are dischargedonto selected locations from an inkjet recording head, typified by apiezo jet recording head, but are not limited to a particular method.However, of these methods, the most preferable method is the methodusing a piezo jet recording head because, economically speaking, itallows formation of a very fine form over a large area with highprecision.

The light-absorption material 102 is formed at locations selected nearboundary portions of individual lens members formed in a later step.FIG. 2(a) illustrates the state of arrangement of the light-absorptionmaterial 102 in plan view. FIG. 2(a) is a plan view in which thetransmissive screen used in the embodiment is viewed from a side fromwhich image light is incident, with a solid line indicating individuallens members 105 and a dotted line indicating the light-absorptionmaterial 102. The light-absorption material 102 is provided near theboundary portions of the lens members 105, and open portions 107 passinglight rays are formed near the center portions of the lens members 105.

FIG. 2(b) is a cross-sectional view of the transmissive screen and animage light path, in a section taken along plane H—H′ of FIG. 2(a).Image light 201 incident upon the lens members 105 is refracted by thelens members 105, passes through the open portions 107, and istransmitted towards an observer. On the other hand, most of the outsidelight 202 from, for example, an illumination lamp disposed in the spaceat the observer side, is absorbed by the light-absorption material 102.Therefore, even if the illumination intensity in the space at theobserver side is high, it is possible to enjoy observing a sharp blackimage having high contrast.

Here, where a top side width 203 of the light-absorption material 102 islarge, the proportion by which the image light 201 is absorbed becomeslarge. Therefore, in order to increase transmittance of the image light,it is preferable to make the top side width 203 to be as small aspossible.

On the other hand, where a bottom side width 204 of the light-absorptionmaterial 102 is made to be as large as possible, the outside lightabsorption effect is high. From the above, it is desirable that thecross-sectional form of the light-absorption material 102 be a taperingform so as to widen towards the light-transmissive substrate 101.

In order to make the bottom side width 204 of the light-absorptionmaterial 102 to be as large as possible, it is desirable for the openportions 107 to be disposed near the focal points of the lens members105. From this viewpoint, the height of the light-absorption material102 is determined.

Next, as shown in FIG. 1(b), lens member compositions 108 are dischargedinto spaces bounded by the light-absorption material 102 from a piezojet recording head 103 in order to form lens precursors 104.

The piezo jet recording head 103 discharges the supplied lens membercompositions from its nozzle by a known inkjet method. To facilitateunderstanding of the embodiment, only one head is shown, but it isobvious that productivity can be increased by disposing a plurality ofheads side by side in order to discharge lens member compositions over alarge area and by performing scanning of the plurality of heads in theentire plane of the light-transmissive substrate 101.

The spaces bounded by the light-absorption material 102 are filled withdrops 108 of the discharged lens member compositions, and the lensmember precursors 104 whose surfaces have been formed into the forms oflenses are formed. The forms of the surfaces of the precursors 104 aredetermined primarily by the viscosities and surface tensions of the lensmember compositions and the wettability of the lens member compositionswith respect to the light-absorption material. From these viewpoints,the chemical composition of the light-absorption material and the lensmember compositions are adjusted.

Although, in FIG. 1(b), a boundary width 109 between the adjacentprecursors 104 is drawn extremely small, from the viewpoint of formingthe forms of the surfaces of the precursors 104, the boundary width 109may be large. However, when the boundary widths 109 are made to be toolarge, the transmittance of the image light is reduced. From thisviewpoint, it is effective to use a method in which different types ofcompositions that do not mix easily with each other are used for thelens member compositions that are discharged from adjacent nozzles 103 aand 103 b. This is because, when this method is used, even if the lensmember compositions spread, the boundaries between the lens members arenaturally formed as a result of the lens member compositions coming intocontact with each other. For the lens member compositions that do notmix easily with each other, a hydrophilic composition may be used forone of the lens member composition types, and a hydrophobic compositionmay be used for the other type of lens member composition. However thelens member composition types which may be used are not limited thereto.

Next, by a post-processing step shown in FIG. 1(c), the precursors 104are formed into the lens members 105 having desired characteristics. Anexample of the post-processing operation may be a hardening reaction by,for example, irradiation of light or heating. However, the type of postprocessing operation is not limited thereto, so that various other typesof post-processing operations may be carried out based on the chemicalproperties of the lens member compositions used. The post processingstep includes not only a hardening reaction, but also post-processing toincrease light transmittance, post-processing to form the precursors 104into more desirable forms, etc. If, after dropping the lens membercomposition liquids, a chemical change occurs as time passes evenwithout performing any processing operation and a desired characteristicis obtained after passage of a certain amount of time, thepost-processing step is omitted. An example of such a case is thatcompositions, which react chemically by mixing two liquids or anaerobiccompositions, are used as the lens member compositions.

The following step is performed to provide the lens members withadditional characteristics. FIG. 1(d) shows an example in which atransparent protective layer 106 is provided at the surface of each lensmember in order to increase the mechanical strength of the transmissivescreen. Here, additional characteristics include, in addition tomechanical strength, increased chemical durability by, for example,anaerobic processing, and the increased optical characteristics basedon, for example, AR coating.

FIGS. 3(a)-3(c) are schematics illustrating the structure of a lensmember used in the embodiment.

FIG. 3(a) shows the bottom surface form (the form of the surface thatcontacts the light-transmissive substrate 101) of the lens member 105,in which, where its horizontal-direction width 301 is WH, and itsvertical-direction width 302 is WV, WH<WV. Such a bottom surface form isdetermined by the planar form of the light-absorption material 102.

The form of the surface of the lens member 105 is determined primarilyby the viscosity and surface tension of the lens member composition andthe wettability of the lens member composition with respect to thelight-absorption material, so that where a horizontal-direction radiusof curvature 303 of the surface of the lens member 105 along plane H—H′shown in FIG. 3(a) is RH, and a vertical-direction radius of curvature304 of the surface of the lens member 105 taken along plane V—V′ is RV,RH<RV.

FIG. 3(b) is sectional view of the lens member 105 taken along planeH—H′, and FIG. 3(c) is a sectional view of the lens member 105 takenalong plane V—V′. As mentioned above, since RH is smaller than RV, theoptical power of the lens member 105 in the H—H′ direction shown in FIG.3(b) becomes large. Spreading of the image light 201 in this directionafter it has exited from the light-transmissive substrate 101 is θH. Incontrast, the optical power of the lens member 105 in the V—V′ directionbecomes smaller. When spreading of the image light 201 in this directionafter it has exited from the light-transmissive substrate 101 is definedas θV, θH>θV, so that it becomes possible to control the viewing angleto be suitable for the viewing-angle characteristics of a human being,which has been described with reference to FIG. 11.

(Second Embodiment of a Method of Producing a Transmissive Screen)

FIGS. 4(a)-4(d) are schematics generally illustrating the steps used inthe second embodiment of the present invention.

As shown in FIG. 2(a), on the light-transmissive substrate 101, lensform restriction patterns 401 are formed by patterning at selectedlocations near the boundary portions of the individual lens members thatare formed in a later step. Examples of the method of forming the lensform restriction pattern 401 by patterning are photolithography andvarious other printing techniques, and a method in which a lens formrestriction material compositions are discharged onto selected locationsfrom an inkjet recording head, typified by a piezo jet recording head,but are not limited to a particular method. However, of these methods,the most preferable method is the method using a piezo jet recordinghead because, economically speaking, it allows formation of a very fineform over a large area with high precision.

It is preferable that, over the entire visible region, the lighttransmittance property of the lens form restriction patterns 401 besubstantially uniform or smooth, and that the light transmittance behigh. By making use of its chemical properties at its surface, the lensform restriction patterns 401 restrict the forms of the lens membersthat are formed in a later step. For example, the pattern surface mayhave a hydrophilic property and the composition of each lens member mayhave a hydrophobic property. Examples are not limited to these.

A film 402 for a light-absorption material is formed at the back side ofthe portion of the light-transmissive substrate 101 where the lens formrestriction patterns 401 are formed.

The film 402 for the light-absorption material is a photosensitive film,and portions thereof upon which light has impinged, and portions thereofupon which light has not impinged, have different chemical and opticalproperties.

Typical examples of such a film are a positive photosensitive adhesivewhich exhibits the property of losing its adhesiveness by being exposed,and chromarin film (produced by E.I. Du Pont de Neumours Inc.), but arenot limited thereto.

Next, as shown in FIG. 4(b), from the piezo jet recording head 103, lensmember compositions 108 are discharged onto the surface of thetransparent substrate bounded by the lens form restriction patterns 401in order to form the lens precursors 104. This step has been describedin detail in the first embodiment, and the description thereof isomitted.

Next, as shown in FIG. 4(c), from the lens member 105 side, thelight-absorption-material film 402 is radiated with an electromagneticwave 403 having a wavelength that causes photosensitive reaction, and byeach lens member 105, the electromagnetic wave 403 converges near thelight-absorption-material film 402 in order to cause aphotosensitization action to occur at selected locations of thelight-absorption-material film 402.

In this step, each lens member 105 may be in the lens precursor state.When a hardening reaction, a light transmittance increasing reaction,etc., are caused to occur by the electromagnetic wave 403, so that achange to a more preferable state can be achieved, the step can besimplified, which is preferable.

Portions 404 where a photosensitization reaction has occurred atselected locations of the light-absorption-material film 402 aretransparent portions, so that image light that has converged by eachlens member 105 passes therethrough. On the other hand, portions 405which have not been exposed exhibit light absorptivity, so that itabsorbs outside light.

When the aforementioned chromarin film is used, the portions 404 where aphotosensitive reaction has occurred lose their adhesiveness, and theadhesiveness of the portions 405 that have not been exposed remains.Therefore, in a post-processing step (not shown), for example, powderhaving light-absorption property is scattered on thelight-absorption-material film 402. Where this is selectively made toadhere to the portions 405 which have not been exposed, it is possibleto form light-absorption-material patterns 406 at selected locations.

As is clear from FIG. 4(c), in the embodiment, the thickness of thelight-transmissive substrate 101 is set so as to be substantially thesame as the light converging distance of each lens member 105. The lightconverging distance is the distance substantially equal to f×n, wherethe focal length of each lens member 105 in air is f, and the refractiveindex of the light-transmissive substrate 101 is n.

(Third Embodiment of a Method of Producing a Transmissive Screen)

FIGS. 5(a)-5(d) are schematics that generally illustrate the steps usedin the third embodiment of the present invention.

First, as shown in FIG. 5(a), a surface treatment layer 501 having hightransparency is uniformly formed on the light-transmissive substrate101. The surface treatment layer 501 has liquid repellency with respectto each of the lens member compositions to be discharged on this layer.In other words, where each of the lens member compositions is ahydrophilic material, it has water repellency, whereas where each lensmember composition is a lipophilic material, it is hydrophilic.

The surface-treatment layer 501 is formed by various thin film formationtechnologies, such as spin coating, dipping, printing, spraying, vapordeposition, sputtering, or forming of a self-organizing film, inaccordance with the physical properties of the material of thesurface-treatment layer 501.

Of these technologies, the thin film formation technology that is usedto form a self-organizing film is suitable for the present inventionbecause the liquid repellency of the self-organizing film can be easilycontrolled and the formation of the self-organizing film does notrequire a special device.

The self-organizing film is a molecular film containing organicmolecules. The organic molecules each contain a functional group whichcan combine with the light-transmissive substrate 101; a functionalgroup, such as a lyophilic group or a liquid-repellent group, providedopposite to the previous functional group, to modify the nature of thesurface of the light-transmissive substrate 101 (that is, controllingthe surface energy); and a normal carbon chain which combines with thesefunctional groups or a carbon chain having a portion thereof branched.These organic molecules combine with the light-transmissive substrate101 and are self-organized in order to form a molecular film, such as amonomolecular film. The self-organizing film contains a bondingfunctional group that can react with constituent molecules of thelight-transmissive substrate 101, and other straight-chain molecules. Itis a film in which compounds, having very high orientation properties byinteraction between the straight-chain molecules, are aligned. Since theself-organizing film is formed by aligning single molecules, it is auniform film on the molecular level. In other words, since the samemolecules are positioned at the surface of the film, the surface of thefilm is uniform and can be provided with surface properties, such asexcellent liquid repellency and a lyophilic property.

Examples of the compounds making up the self-organizing film includealkylsilanes containing an alkyl group or fluoroalkylsilanes, such asheptadecafluorotetrahydrodecyltriethoxysilane ortrifluoropropyltrimethoxysilane. The self-organizing film is disclosedin detail in, for example, “An Introduction Ultrathin Organic Films,”Ulman, Academic Press.

When the surface-treatment layer 501 is formed using the self-organizingfilm, any one of the aforementioned material compounds and thelight-transmissive substrate 101 are placed in the same sealedcontainer. When the temperature is ordinary temperature, thesurface-treatment layer 501 is formed by leaving it for a few days. Bymaintaining the whole sealed container at a temperature of approximately100° C., the surface-treatment layer 501 can be formed approximatelythree hours. In this way, since the step of forming thesurface-treatment layer 501 using a self-organizing film is very simpleand does not require a special device, this step is particularlysuitable for producing a large transmissive screen.

A light-absorption film 502 is formed on the back side of the surface ofthe light-transmissive substrate 101 where the surface-treatment layer501 is formed. The light-absorption layer 502 is formed of a materialwhich has a smooth light transmittance in the visible region and whichhas high absorptivity with respect to laser light. In accordance withthe physical properties of the material of the light-absorption layer502, the light-absorption layer 502 is formed by various thin filmformation technologies, such as spin coating, dipping, printing,spraying, vapor deposition, sputtering, or forming of a self-organizingfilm.

Then, as shown in FIG. 5(b), from the piezo jet recording head 103, lensmember compositions 108 are discharged onto the surface of thelight-transmissive substrate 101 where the surface-treatment layer 501is formed, thereby forming the lens precursors 104. However, since,unlike the first and second embodiments, there are no structures orpatterns that separate adjacent lenses, special considerations arerequired to form individual lens members separately.

FIG. 6(a) shows the relationship between the diameter of a lensprecursor 104 and a landing target location 601 of the lens membercomposition on the light-transmissive substrate 101. After the lensmember compositions 108 have landed near the landing target locations601, they run out and spread by contact angles determined by therelationship between their wettability with respect to thesurface-treatment layer 501, thereby forming the lens precursors 104having curvatures determined by the surface tensions of the lens membercompositions 108. The planar forms of the precursors 104 aresubstantially circular having diameters SP with the correspondinglanding target locations 601 being the substantial centers thereof.Therefore, as shown in FIG. 6(b), when an interval P between adjacentlanding target locations 601 is such that P>SP, individual lensprecursors 104 that are separated from each other can be formed. When Pis excessively larger than SP, the dead spaces between the lensprecursors 104 become large, thereby reducing the light transmittance ofthe transmissive screen, so that this is not preferable. In addition, asshown in FIG. 6(c), when the interval P between adjacent landing targetlocations 601 is set so that P<SP, after the lens member compositions108 have landed, the adjacent lens member compositions coalesce, so thatseparate individual lens precursors cannot be formed.

Therefore, when a pitch PN between the adjacent nozzles 103 a and 103 bof the piezo jet recording head 103 is such that PN>SP, it is possibleto separately form adjacent individual lens precursors 104. Although theexample of adjusting the pitch PN between the adjacent nozzles has beendescribed above, it is obvious that the same advantages can be obtainedby suitably controlling a scanning pitch of the piezo jet recording head103 by setting the pitch PN between the adjacent nozzles to be adistance that is different from the pitches between the adjacent lensprecursors 104.

In addition, it is possible to control the viewing angle of thetransmissive screen by positively fusing the adjacent lens precursors104 into an integral structure.

FIG. 7(a) illustrates the arrangement of nine adjacent landing targetlocations 601. A horizontal-direction pitch PH between adjacent landingtarget locations 601 is set so that PH>SP, while a vertical-directionpitch PV is set so that PV<SP. Each lens member composition 108 isdischarged onto and lands on each of these landing target locations 601,so that, as shown in 7(b), the lens precursors 104 having planar formsthat are individually and separately formed in the horizontal directionand having fused forms in the vertical direction are formed. With regardto the curvature of each lens member obtained from its correspondinglens precursor 104, where the horizontal-direction radius of curvatureis RH and the vertical-direction radius of curvature is RV, RH<RV. Asdescribed in the first embodiment, the spreading of image light that haspassed through each lens member is wider in the horizontal direction inconformity with the viewing angle characteristic of a human being, sothat it possesses a viewing angle characteristic that is narrow in thevertical direction.

The pitches between the landing target locations 601 do not have to beuniform over the entire transmissive screen, so that they can be freelyset based on desired characteristics. For example, with thevertical-direction pitches made variable, the number of lens membercompositions that are fused can be controlled in order to adjust thevertical viewing angle or the regularity of the pitches in thehorizontal and vertical directions can be reduced in order to reducemoiré that occurs due to the interaction between the image light and theoptically regular patterns of the lens members.

Next, as shown in FIG. 5(c), laser light 503, having an intensity equalto or greater than a threshold value that causes, in its convergedstate, fusion/evaporation or abrasion of the material of thelight-absorption layer 502, is caused to impinge from the lens member105 side, and to converge near the light-absorption layer 502.Fusion/evaporation or abrasion is caused to occur at selected locationsof the light-absorption layer 502 near the converging portion of thelaser light 503, thereby forming open portions 504. In this step, eachlens member 105 may be in a lens precursor state, and if, for example, ahardening reaction or a light transmittance increasing reaction iscaused to occur by the laser light 503, so that changes to a morepreferable state are achieved, the step can be simplified, which ispreferable.

The open portions 504 of a light-absorption-material pattern 506 passthe image light that has been converged by each lens member 105. Un-openportions 505 exhibit light absorption, so that they absorb outsidelight.

As is well known, it is necessary for the laser light to have a highenergy value in order to cause fusion/evaporation or abrasion to occurat the laser light absorption material. Examples of lasers which producesuch laser light are an excimer laser using, for example, XeF; an Nd:YAGlaser; a Ti:Al₂O₃ laser and a laser producing light obtained afterharmonic and wavelength changes thereof have been made; and a dye laser.In order to irradiate the large-area light-transmissive substrate 101with intense laser light over the entire area thereof, scanning theentire area with a small-area laser light spot by light-deflecting meansis effective from the viewpoints of preventing the laser device frombecoming large in size and complicated.

(Fourth Embodiment of a Method of Producing a Transmissive Screen)

FIGS. 8(a) and 8(b) are schematics generally illustrating the steps usedin the fourth embodiment.

As shown in FIG. 8(a), from the piezo jet recording head 103, avolume-type phase device composition 801 is discharged onto the backside of the surface of the light-transmissive substrate 101 where thelight-absorption-material pattern 102 and the lens members 105 havealready been formed, thereby forming a volume-type phase deviceprecursor 802.

The volume-type phase device precursor 802 is formed of a materialhaving high light transmittance, that is substantially uniform or smoothover the entire visible region, and has a random form and arrangementdistribution, which are determined in accordance with the extent towhich the coherence of image light is reduced. Such a form andarrangement distribution are provided by randomly changing the liquidamount of the volume-type phase device composition 801 discharged fromthe piezo jet recording head 103 or by randomly changing the scanningdirection and scanning amount of the piezo jet recording bead 103.

Next, as shown in FIG. 8(b), the volume-type phase device 803 isprovided with more preferable characteristics by, for example, hardeningthe volume-type phase device precursor 802 by light irradiation,heating, or the like.

In this way, by forming the volume-type phase device 803 on the backside of the surface of the light-transmissive substrate 101 where thelens members 105 are formed, the coherence of image light can bereduced, so that it is possible to enjoy observing a high-quality imagehaving few speckles.

(Fifth Embodiment of a Method of Producing a Transmissive Screen)

Although in the first to fourth embodiments the lens member compositionsor the volume-type phase device composition have been described byreferring to optically transparent materials which can be discharged bythe piezo jet recording head as an example, it is possible to mix verysmall particles having light diffusing property in order to furtherincrease the light diffusion action of each lens member. Examples ofsuch very small particles are glass beads, styrene beads, and acrylicbeads, which have average particle diameters of the order of a fewmicrons to 20 microns. However, the types of very small particles arenot limited to these examples.

The above-described lens member compositions are applicable to any oneof the first to fourth embodiments, and are effective structuralmaterials to adjust the viewing angle of the transmissive screen.

(Modifications)

The present invention is not limited to the above-described embodiments,so that various modifications and changes may be made within a scope notdeparting from the gist of the present invention.

For example, although the piezo jet recording head has been referred toas the head member which discharges drops of, for example, lenscompositions, other inkjet recording heads having similar functions maybe used. A typical example is a bubble jet recording head.

In addition, although the bottom surface of each lens member has beendescribed as having a rectangular form, it may have a circular form, anelliptical form, or an indeterminate form, for example.

Further, although the light-absorption-material patterns have beendescribed as having tapered forms in cross section, they may haverectangular parallelepiped forms or curved forms in cross section.

INDUSTRIAL APPLICABILITY

As described in detail above, according to the present invention, thereis provided a method of producing a transmissive screen having astructure including light-absorption-material patterns that are formedat locations corresponding to locations of lens members, which areprovided side by side on a light-transmissive substrate, andcorresponding to locations of boundary portions between the lensmembers. In this method, very small droplets of lens compositions aredischarged onto and land on the light-transmissive substrate. By thedroplets of the lens compositions, the lens members or precursorsthereof are formed. This makes it possible to realize, at a low cost, abright transmissive screen which has high contrast and which can displaya high-quality image having reduced moiré and reduced or few speckles.

1. A method of producing a transmissive screen having alight-transmissive substrate, lens members and light-absorption-materialpatterns, comprising: forming the light-absorption-material patterns;forming lens form restriction patterns; discharging lens compositions ofat least one of the lens members or precursors of the lens memberstowards the light-transmissive substrate; and forming the lenscompositions into the lens members as boundary portions of theprecursors of the lens members are formed over thelight-absorption-material patterns, and as the light-absorption-materialpatterns are formed.